Hydraulic pumps or hydraulic motors of this kind are used in many different connections. A common feature with such pumps or motors is, inter alia, that a change in the displacement or transmission ratio between pump and motor requires the exchange of whole units, or in the best of cases a plurality of components, although even this normally requires the pump or motor to be completely dismantled. In this respect, it is also often necessary to disconnect the external hydraulic lines. Another disadvantage with these known pumps and motors is that the hydraulic-oil connections are arranged axially in relation to the pump housing or motor housing, which often causes difficulty in assembly and/or in drawing the hydraulic lines.